Abstract: :
Purpose:Assess and compare the fatty acid composition of membranephospholipids of the corneal epithelium and stroma of the NZArabbit with that of human cadaver tissue.Methods: Corneas were dissected, placed on an ice–coldglass surface and corneal buttons (0.71cm2) were prepared witha trephine. The epithelium and stroma was isolated and extractedwith a mixture of CHCl3/CH3OH as described by Bligh and Dyer1.Lipids were separated by TLC. The phospholipid fraction wasisolated and trans–esterified (4% H2SO4 in methanol).The fatty acid methyl esters formed were extracted and quantifiedby gas liquid chromatography with the aid of appropriate internalstandards.Results: Membrane phospholipids of the corneal epithelium ofthe rabbit exhibited a simple fatty acid composition with palmitate(C16:0; 38.2 mole%), stearate (C18:0 = 19.8 mol%) and oleate(C18:1; 42.0 mol%) being the only phospholipid fatty acyl chains.This was in contrast to the stroma which exhibited notable quantitiesof both C18:2 (7.1 mole%) and C20:4 (3.2 mol %), in additionto the saturated and monoenoic acids found in the epithelium.A similar fatty acyl chain pattern to the rabbit was evidentin phospholipids of the stroma of human cadaver tissue, withC18:2 and C20:4 reaching levels up to 2.4 mol% and 4.3 mol%,respectively. C18:0 was the major saturated fatty acyl chainof phospholipids of both the epithelium and stroma. The moststriking difference between the rabbit and human cornea wasapparent in the phospholipid C18:2 and C20:4 fatty acyl chainabundance of the epithelium. While rabbit corneal epitheliumwas devoid of C18:2 and C20:4, phospholipids of the human cornealepithelium showed considerable variability in C18:2 and C20:4abundance, ranging from non–detectable to as high as 18.2mole%.Conclusion:The fatty acid profile of phospholipids of the cornealstroma of the NZA rabbit is similar to that of human cadavertissue with minor differences in relative abundance. The cornealepithelium of the rabbit, however, appears to be distinct fromthat of the human by the absence of both C18:2 and C20:4. Bothacids were detected in human tissue. However, their abundancewas highly variable presumably due to nutritional influences.